newsequentialid

The goal of using a sequential guid is so you can use clustered indexes without the high levels of fragmentation that would normally exist in a clustered index if it was a regular guid, correct? Yes, you are correct. First to clarify, a primary key and clustered index are 2 separate and distinct things, i.e. one is not coupled to the other (PKs can be nonclustered, clustered indexes can be non-PKs). That given, I think you're asking more "Should a Sequential GUID be used as a clustered index". That's a loaded question, but Kimberly Tripp has discussed this probably the best of anyone I've seen

Is there any way to implement the Guid COMB identity strategy for objects in the new Entity Framework 4.1 using the CodeFirst design? I thought setting the StoreGeneratedPattern would work, but it still gives me normal GUIDs. I guess you are using SQL server as your database. This is nice example of inconsistency among different MS tools. SQL server team doesn't recommend using newid() as default value for UNIQUEIDENTIFIER columns and ADO.NET team use it if you specify Guid property as autogenerated in the database. They should use newsequentialid() instead! If you want sequential Guids